Summary of Work: Diet may affect the risk of several chronic human diseases but additional research is needed. This project has two main thrusts. One is the study of diet-cancer relations; the other is the study of diet in relation to risk of amyotrophic lateral sclerosis (ALS). The diet-cancer relations under investigation are vegetable intake in relation to risk of breast cancer, studies of alcohol drinking patterns in relation to risk of breast cancer, and studies of eating frequency in relation to risk of colorectal cancer. Additional related work is listed in the list of publications. The present emphasis is on analysis of existing data resources (the National Health and Nutrition Examination Survey Epidemiologic Follow-up Study, the Cancer and Steroid Hormone Study, and other studies). Defects in antioxidant defences (e.g., superoxide dismutase 1 [SOD1]) are a cause of ALS, thus it is reasonable to suspect that antioxidant intake may also affect the incidence or progression of this disease. Regarding diet and ALS, one thrust is an analysis of dietary data from Dr. Kamel's case-control study of ALS. A second project on diet and ALS is in a developmental stage. The goal is to determine the feasibility of studying the relation in a large cohort study underway at the National Cancer Institute. The cohort consists of members of the American Association of Retired Persons (AARP) who have completed a dietary questionnaire (approximately 600,000 people). We expect about 150 cases of amyotrophic lateral sclerosis to develop in this cohort by 2002.